1. Field of the Invention
The present invention relates to an electronic flash apparatus with a power control switch, and more particularly to an electronic flash apparatus having a manual power control switch and adapted for use with a camera wherein the control switch is positioned to be reachable by the camera-operating hand of the user when such hand is in a normal position to operate the camera.
2. Description of the Prior Art
Electronic flash units for providing artificial illumination during photographic exposures occuring under conditions of low ambient scene light intensity are well known in the art. Such electronic flash units are generally adapted to receive an external, substantially steady state, d-c battery voltage which powers a voltage converter in a conventional manner to convert the d-c voltage which may be in the order of 6 volts, to a suitable flash operating voltage. A charging current from the voltage converter is directed to a storage capacitor so as to gradually charge the storage capacitor to a d-c voltage which may be in the order of 350 volts. Means are also provided for selectively discharging the storage capacitor through a flash discharge tube to produce the photographic illuminating flash of light. An on/off switch may also be provided to control the power connection from the battery to the voltage converter. Thus, when a photographer anticipates using the electronic flash, he must initially turn on the on/off switch to power the voltage converter and thereafter wait a short period of time for the storage capacitor to become fully charged. After the storage capacitor in the electronic flash is discharged through the flash tube during a photographic exposure operation of the camera, the voltage converter will automatically operate to recharge the storage capacitor in anticipation of a subsequent photographic exposure unless the operator consciously remembers to turn off the on/off switch. Should the operator fail to consciously turn off the on/off switch and let the camera sit idle for a period of time, the voltage converter will continue to operate to maintain the charged condition of the storage capacitor thereby providing a constant current drain on the battery. A prolonged period of idleness with the on/off switch remaining on may ultimately result in the complete drainage of the battery so as to render the battery inoperative.
One approach to solving this problem has involved the use of a time-out circuit within the electronic flash so as to automatically disconnect the battery from the voltage converter if the flash is not fired within a prescribed time period. However, such a time-out circuit generally involves the use of a power transistor in series connection between the battery and voltage converter which decreases the actual power input to the voltage converter as a result of the high power losses inherent to the power transistor.
A so-called "two-button camera" having an integral flash unit built therein has been disclosed in U.S. Pat. No. 4,007,469 entitled "Photographic Apparatus", by E. H. Land, issued Feb. 8, 1977 in common assignment herewith. This two-button camera embodies a so-called "grip switch" in the base portion thereof to turn on the electronic control circuit associated with both the camera and the electronic flash when the camera is held by the user. However, electronic flash units are generally configured to be detachable from the top of the lens housing portion of the camera thereby making it inconvenient for a grip switch, which constitutes an integral part of the camera, to control the detachable electronic flash unit. Since the electronic flash unit is normally connected above the shutter housing of the camera, it has also heretofore been inconvenient to provide the electronic flash unit with its own grip switch since most cameras are not normally held above their shutter housings.
More recently, an electronic flash unit, which is attachable to a camera, and includes a switch for controlling the charge to the storage capacitor of the flash unit, has been disclosed in a copending U.S. patent application, Ser. No. 749,313 now U.S. Pat. No. 4,085,414 entitled "Electronic Grip Switch Arrangement" by J. Burgarella et al, filed Dec. 10, 1976 in common assignment herewith. The switch is operated by a laterally displaceable on-off control arm which extends from the flash unit atop the camera downwardly into engagement with the user's camera support or holding hand when such hand holds the camera in a normal operational manner. With such an arrangement, when the camera is so held by the user's support hand, the control arm and thus the switch is tripped and power is applied to the storage capacitor and when the camera is released the control arm is released and the so-applied voltage is shut off.
Although the above-described control arm-switch arrangement is useful and adequate for conserving excess current drain in charging such storage capacitor, a shortcoming thereof is that the capacitor charging circuit can be activated inadvertently in handling the camera and flash unit. Further, the control arm must be unfolded and can interfere with the facile and comfortable handling of the flash-equipped camera.
However, a battery conserving on-off storage capacitor switch for an electronic flash unit is useful and economical and there is a need and market for a storage capacitor charging switch that significantly overcomes the above prior art shortcomings.
Accordingly, it is a primary object of this invention to provide a flash unit storage capacitor charge control apparatus which is so positioned with respect to a flash unit and associated camera as to minimize the inadvertent activation of such control apparatus and thus the unintended or prolonged application of power to the storage capacitor of the flash unit by the user's picking up or supporting, in a normally expected manner, the camera and flash unit. The battery associated with such a camera and flash unit is thus conserved. Further, such charge control apparatus is readily reachable by the user's camera operating hand, when such hand is in a normal position to operate the camera.
Other objects of this invention will be in part obvious and will in part appear hereinafter. The invention accordingly comprises the mechanism and system possessing the construction, the combination of elements and the arrangement of parts which are exemplified in the following detailed disclosure.